The platform of the midair boxes is not prominent enough, and looks like the shadow of the box
The collision of the boxes is very unclear. Sometimes the game registers a hit even when the chicken is about 1 box distance away from the actual box graphic, be it behind or in-front.
The background scrolls faster than the obstacles which doesn't make sense. If the depth difference between the background and obstacles is inconsequential, the background should move at the same speed as the obstacles. If the depth difference between the background and obstacles is significant, it should move slower, not faster, than the obstacles.
The background is too prominent, its color saturation is too similar to the obstacles.